This invention relates to improvements in guidewires, particularly guidewires used in small bore blood vessels such as those involved in angioplasty procedures. U.S. Pat. No. 4,545,390 to Leary discloses a small diameter (no greater than about 0.020" in diameter) steerable guidewire which can be advanced and steered into and along very narrow blood vessels to locate the distal end of the guidewire in a precise position in a selected blood vessel branch. Once the guidewire has been so placed, a catheter can be advanced over the guidewire directly to the desired location in the patient's cardiovascular system to enable the catheter to perform its intended function at that location. For example, such guidewires are particularly useful in coronary angioplasty procedures in which a small diameter balloon dilatation catheter is placed in a narrowed region of a coronary artery so that the balloon may be inflated to widen the lumen of the artery and improve blood flow through the artery.
U.S. Pat. No. 4,545,390 to Leary discloses a small diameter steerable guidewire which is capable of transmitting from its proximal end to its distal end substantially all of the angular rotation applied to the proximal end. The distal end of the guidewire is adapted to be bent to a set curve by the surgeon before the guidewire is placed in the patient. After the guidewire has been placed in the patient's blood vessel, it may be steered to select between branches of the patient's cardiovascular system by rotating the proximal end of the guidewire to direct selectively the bent distal end of the guidewire to the desired branch. Typically, the guidewire is advanced through the blood vessels while being monitored fluoroscopically.
The curve which the physician forms at the distal tip of the guidewire, before inserting it into the patient, necessarily involves an approximation as to the degree of curvature best suited for the particular procedure to be performed. Sometimes, after the guidewire has been placed, the degree of bend placed in the distal tip proves to be too great or too little to enable the tip to be steered into a selected blood vessel. Under those circumstances, the physician may have to withdraw the guidewire, reform the bend at its distal tip and then reinsert the guidewire. That complicates and delays the procedure undesirably. In order to overcome that limitation, a small diameter steerable guidewire was developed in which the degree of curvature at the distal tip of the guidewire could be adjusted and controlled while the guidewire remained in place in the patient and without requiring removal and manual reshaping of the guidewire. Such a guidewire is disclosed in U.S. Pat. No. 4,719,924 to Crittenden et al. and includes an elongate torsionally rigid shaft formed from a solid walled tube. The distal end of the guidewire includes a core wire that is attached to and extends from the distal end of the solid walled tube and the helical coil arrangement that extends about the core wire. A pull wire extends through the full length of the guidewire and is connected at its distal end to the distal end of the spring. The proximal end of the pull wire extends through the spring arrangement and into the solid walled tube and exits at the proximal end of the shaft. An arrangement is provided at the proximal end of the guidewire to vary the tension on the pull wire to cause the distal end of the guidewire to assume a degree of curvature depending on the extent of pull applied to the pull wire.
Also among the desirable features in guidewires is the ability to extend the length of the guidewire, from its proximal end, in order to facilitate catheter exchanges over the guidewire. As described in U.S. Pat. Application Ser. No. 206,008, filed June 13, 1988, the proximal end of the guidewire that extends out of the patient is relatively short. In order to exchange the indwelling catheter for a different catheter, for example, to use a different size balloon, an extension wire may be attached to the proximal end of the guidewire that extends out of the patient. The extension wire is of a length such that its total length, together with the exposed length of the proximal end of the indwelling guidewire is greater than the length of each of the indwelling and replacement catheters. Thus, when the catheter is withdrawn, some portion of the guidewire will be exposed and grippable by the physician or an assistant in order to assure that the position of the guidewire in the patient will be maintained during the catheter exchange procedure. As described in Application Ser. No. 206,008, the proximal end of the guidewire and the distal end of the extension wire are provided with connector means by which they may be detachably connected. The connector means is such that it does not present an enlarged cross sectional configuration greater than that of the guidewire itself in order that the catheters may be advanced smoothly over the connected wires. To that end, the connector element on the proximal end of the guidewire is in the form of a slender tubular member defining a socket which is receptive to a small diameter latching arrangement carried by the distal end of the extension wire, the latching arrangement being insertable in and mechanically interlockable with the tubular socket.
Although it would be desirable to provide a guidewire having the ability to adjustably control the curvature at the distal tip of a guidewire while also providing a capability for attaching an extension wire to permit catheter exchanges to be performed, those objectives have not been achievable previously in the same guidewire because the control device for operating the pull wire necessary for the adjustable J feature would not permit connection of a guidewire extension or provide a low profile over which catheters could be advanced in order to perform a catheter exchange. It is among the objects of the invention to provide such a guidewire having both capabilities.